Number of ways to build a contiguous building with n LEGO blocks of size 1 X 3 on top of a fixed block of the same size so that the building is symmetric after a rotation by 180 degrees.
A123775
Number of ways to build a contiguous building with n LEGO blocks of size 1 X 3 on top of a fixed block of the same size so that the building is symmetric after a rotation by 180 degrees.
Terms
- a(0) =2a(1) =8a(2) =24a(3) =115a(4) =451a(5) =2474a(6) =10377a(7) =60048a(8) =268402a(9) =1600292a(10) =7416480
External references
- oeis: A123775